Author(s): Dekui Yuan; Binliang Lin; Jianhua Tao; Sun Jian
Linked Author(s): Dekui Yuan, Jianhua Tao, Binliang Lin
Keywords: Longitudinal dispersion; Water wave; Diffusion coefficient; Sigma coordinates 1
Abstract: This paper presents an investigation of the relationship between short period water waves and the dispersion of a pollutant in the 2-D vertical plane using both analytical and numerical methods. The transport and mixing of the pollutant in a water wave field due to the movement of fluid particles was first studied analytically. It was found that in the wave field the transport and mixing of pollutant was anisotropic, in additional to being affected by the drift velocity. An advective-diffusion numerical model was then developed on a Sigma coordinate system to simulate the solute transport process in a wave field. The effect of the wave parameters on the dispersion of a pollutant was investigated by varying key wave parameters. Details are given of the method developed for determining the longitudinal dispersion coefficient using the numerical model predicted concentration distributions. The relationship between the distribution of the diffusion coefficient and the mixing of a pollutant was also studied. The results show that: (a) the value of the longitudinal dispersion coefficient increases substantially as the vertical diffusion coefficient decreases, but it is only moderately affected by the horizontal diffusion coefficient, and (b) the vertical distribution of the diffusion coefficient affects only slightly the value of the longitudinal dispersion coefficient. Thus a depth averaged vertical diffusion coefficient can be used for predicting the mixing and dispersion of a pollutant in the water wave field.
Year: 2007